1. Field of the Invention
The present invention relates to a ceramic member controlled with respect to a form of the surface, and a method of producing the same, and more in detail to such a ceramic member formed on the surface with fine protrusions for easily adhering or attaching heterogeneous substances and a method of producing the same.
2. Description of the Related Art
For example, in the course of producing process of semiconductor device, a fine processing step is generally composed in a film forming process as PVD or CVD, or an etching process using a corrosive gas. A rate of occupying the producing process trends to increase in company with of the processing degree of the semiconductor becoming finer and more complicated. Since the film forming process and the etching process are subjected to severe conditions such as vacuum, plasma atmosphere or high temperatures, ceramic materials having corrosion resistance are employed as a processing container exposed to plasma.
FIG. 14 is a cross sectional view showing a schematic structure of a helicon wave plasma etching. In FIG. 14, reference numeral 1 designates an etching process chamber having an etching gas supply 2 and a vacuum outlet 3, and around the outer circumference of the process chamber 1, there are installed an antenna 4, an electromagnet 5 and a permanent magnet 6. Within the process chamber 1, a lower electrode 8 is disposed for supporting a semiconductor wafer 7 as a material to be processed. The antenna 4 is connected to a first high frequency source 10 via a first matching network 9, while the lower electrode 8 is connected to a second high frequency source 12 via a second matching network 11.
The etching process depending on the etching apparatus is carried out as follows. The semiconductor wafer 7 is set on the lower electrode 8 and the interior of the etching process chamber 1 is made vacuum, followed by supplying an etching gas from the etching gas supply 2. Subsequently, the antenna 4 and the lower electrode 8 are supplied with a high frequency current of e.g., 13.56 MHz from the high frequency sources 10, 12 via the corresponding matching networks 9, 11. On the other hand, a desired current is applied to the electromagnet 5, thereby to generate a plasma of high density within the etching process chamber 1. By this plasma energy, the etching gas is decomposed into an atom like state, and the etching process is carried out on a film formed on the semiconductor wafer 7.
By the way, in this kind of the producing apparatus, as the etching gas, employed are chlorine based gases as carbon tetrachloride (CC14) or boron chloride (BC13), otherwise fluorine based gases as carbon fluoride (CF4, C4F8), nitrogen fluoride (NF3) or sulfur fluoride (SF6). Accordingly, there is a reason for requesting plasma resistance for the composing members such as the interior walls of the etching treatment chamber 1 exposed to the plasma under the corrosive gas atmosphere.
As the composing member requesting the plasma resistance, known is a ceramic sintered substance containing at least one kind as a main element, for example, in the second A group or third A group of the periodic table and having the surface roughness (Ra) being 1 μm or less and the porosity being 3% or lower (JP-A-10-45461). Another ceramic sintered substance is proposed which is formed, on the surface thereof to be exposed to the plasma, with a sintered substance of yttrium aluminum garnet of the porosity being 3% or lower, said surface being made 1 μm or less in average roughness (Ra) of the centerline (JP-A-10-236871). Incidentally, since the using parts of the plasma resistant member are of a vacuum system and at high temperatures, it is important that the using parts do not give bad influences to an atmosphere, and for example, they work inconveniently to a gas releasing property. Herein, a gas adsorption is meant by adsorbing a portion of the gas existing on the surface of the member, and as the amount of the gas adsorption is in proportion to a surface area, it is desirable that the surface is flat, taking the gas releasing property into consideration.
By the way, the film forming means utilizing the plasma energy and the etching means are involved with problems as mentioned under. For example, during forming the film, not only faces formed with the film but also the interior wall of the process chamber exposed to the plasma and faces of supporters supporting the base material formed with the film are accidentally adhered and piled with film forming particles. Phenomena occur, that parts of the film forming components adhered and piled on the interior wall and the supporting faces peel or exfoliate from the adhered faces, and small particles attach to the face formed with the film.
Re-adhesion of small particles separating from the interior wall of the process chamber interrupts the film forming for such as a circuit pattern during forming, or deteriorates quality, resulting in causing decrease of reliability or yield of the film formed products. For giving ability of preventing particle from separation, there has proposed means of making coarse the surface of the plasma resistant member composing the interior wall of the treatment chamber (JP-A-2000-191370). That is, the known means depends on a blasting treatment, so that the surface is coarsened to exceed 1 μm in the surface roughness (Ra) so as to strengthen physical connection with the adhered and piled films and lessen peeling from the surface (anchoring effect).
However, the coarsening means by the blast treatment has a problem in regard to the gas releasing property, cannot give an enough anchoring effect to the ceramic surface, and still leaves the problem of particle separation unsolved. Namely, since the coarsened surface by the coarsening means is rugged where groove-like or wave-like surface areas are broadly enlarged and flared outside (V shape in cross section), though exhibiting the anchoring effect, this effect is insufficient, and it is demanded to heighten and improve the preventing ability of particle separation. Further, since the enlargement of the areas by making the rugged surfaces and by existence of fine flaws generated owing to the blast treatment acts on the gas adsorption in the process chamber, separation and release of the adsorbed gas, the enlargement probably gives bad influences to the film forming. In addition, surfaces while being damaged immediately before exfoliation by the blasting treatment peel owing to temperature change at service thereof and have inconveniences causing particles of the surface itself of the ceramic member.
Further, a blast treatment invites decreases in mechanical strength of the ceramic material and in plasma resistance. The decrease in mechanical strength raises problems such as breakage by thermal strain while forming films particularly in a CVD process accompanying a heating. On the other hand, a plasma resistance adopts a unit for removing fine flaws from the surface by such as a mirror process, but this is defined in shapes of the ceramic material. Namely, a plane ceramic member is easily subjected to the mirror process, but in the case of three dimensionally complicated shapes, a whole removal of fine flaws is in fact extremely difficult.
Also in the etching process, at parts other than ranges directly exposed to the plasma within an chamber, products produced by reaction with the plasma are piled. Accordingly, the interior of the chamber is periodically cleansed for avoiding inconveniences brought with generation or separation of particles.